Turbine assembly for a turbocharger, having two asymmetric volutes that are sequentially activated, and associated method

ABSTRACT

A turbine assembly for an exhaust gas turbocharger has separate first and second volutes that are sequentially activated via a valve that receives exhaust gases from an engine. In a first position of the valve, only the first volute receives exhaust gas; in a second position, both volutes receive exhaust gases. In a third position, a bypass passage is also opened so that some exhaust gas bypasses the turbine wheel. Unlike conventional twin-scroll turbines, each volute receives exhaust gases from all engine cylinders, and the first volute feeds gas into the B-width portion of the wheel, while the second volute feeds gas into the wheel after the contour portion.

BACKGROUND OF THE INVENTION

The present disclosure generally relates to turbochargers for internalcombustion engines, and more particularly relates to a turbine assemblyfor a turbocharger, and to a method for operating a turbochargedinternal combustion engine system.

A turbine assembly of a turbocharger for an internal combustion enginegenerally must be able to operate with acceptable performance over arange of exhaust gas flow rates as engine operating conditions change.Depending on the engine characteristics, in some cases this requires afairly sophisticated variable-geometry nozzle in the turbine assembly toregulate the flow of exhaust gas into the turbine wheel as the engineoperating condition changes.

In some applications there is a desire to avoid such variable-geometrynozzles and instead use a simpler fixed-geometry turbine nozzle. Thechallenge presented in some cases is achieving a sufficiently wide flowrange capability with the fixed geometry.

BRIEF SUMMARY OF THE DISCLOSURE

The present disclosure is directed to a turbine assembly suitable for(though not necessarily limited to) fixed-geometry turbines, and able toachieve a relatively wide flow range capability. A turbine assembly inaccordance with one embodiment described herein comprises a turbinehousing having an exhaust gas inlet for receiving exhaust gas from theengine, a bore for conducting a flow of exhaust gas out of the turbinehousing in an axial direction, and a twin volute surrounding the bore,the twin volute comprising a first volute and a second volute that isdivided and separated from the first volute. The first volute isconnected to and receives exhaust gas from the exhaust gas inlet. Theturbine assembly further includes a turbine wheel rotatably mounted inthe bore.

The first volute has an outlet portion configured to direct exhaust gasinto a first portion of the turbine wheel, while the second volute hasan outlet portion configured to direct exhaust gas into a second portionof the turbine wheel located downstream of the first portion of theturbine wheel with respect to the axial direction.

The turbine assembly also includes a valve arranged to receive exhaustgas from the engine, the valve defining a valve cavity connected to thesecond volute but not to the first volute. The valve further comprises avalve member movable between a first position allowing exhaust gas toflow to the first volute but preventing exhaust gas from flowing fromthe valve cavity to the second volute, and a second position allowingexhaust gas to flow to the first volute and to flow from the valvecavity to the second volute.

Thus, the first and second volutes are sequentially activatable byadjusting the position of the valve. At relatively low exhaust gas flowrates, all of the exhaust gases from the engine can flow to the firstvolute only, and the second volute is inactive. At higher flow rates,the valve can be opened to allow some of the total exhaust gas flow topass into the second volute, such that both volutes are active.

In one embodiment, there is also a bypass passage connected between thevalve cavity and the bore of the turbine housing downstream of theturbine wheel, and the valve member is movable into a third positionallowing some of the total exhaust gas flow to pass through the bypasspassage into the bore. In this condition, both volutes are active andadditionally there is bypass of exhaust gas around the turbine wheel.This arrangement allows a greater flow rate than could be achieved ifall of the exhaust gas had to pass through the turbine wheel.

In some embodiments of the turbine assembly, the second volute can havea larger volume, or more precisely, a larger A/R ratio, than the firstvolute. The A/R ratio is a ratio between the volute's cross-sectionalflow area and the radius at the centroid of that area, as measured fromthe turbine wheel's rotational axis. An advantage of this arrangement isthat the first volute can be sized relatively small so it is optimizedfor low-flow conditions in which only the first volute is activated;when a greater amount of exhaust gas flow must be passed, the secondvolute can be activated, and the second volute can be designedspecifically for such higher-flow conditions.

Unlike a conventional twin-scroll turbine assembly, the turbine assemblydescribed herein can be used with engines having an odd number ofcylinders, because all engine cylinders feed their exhaust gases as acommingled stream that is then supplied into the first volute alone (atlow-flow conditions), or into both the first and second volutes (athigher-flow conditions), or into both volutes and into the bypasspassage (at highest-flow conditions). In contrast, conventionaltwin-scroll turbines are typically used only for engines with an evennumber of cylinders because half of the cylinders feed one of thescrolls and the other half of the cylinders feed the other scroll.

The turbine assembly described herein further differs from conventionaltwin-scroll turbines in the way the scrolls or volutes are arranged withrespect to the “B-width” and “contour” portions of the turbine wheel.The B-width portion is the largest-diameter portion of the wheel formedby the leading edges of the turbine blades, and typically is linear ornearly linear as viewed in a radial-axial projection of the wheel. TheB-width of the wheel is the axial length of the B-width portion inradial-axial projection, and is a rough measure or indication of themaximum-flow capacity of the wheel. The B-width portion, as viewed inradial-axial projection, may be substantially constant in diameter inthe axial direction, or it may be of the “mixed-flow” type such that itsdiameter decreases in the downstream axial direction. The turbine wheeltypically has a “contour” portion following the B-width portion, and afinal portion following the contour portion. The contour portion asviewed in radial-axial projection typically is concave in the radiallyoutward direction. The throat (minimum flow area) of each blade passageis located in the final portion of the wheel. In a conventionaltwin-scroll turbine, both scrolls feed exhaust gas into the B-widthportion of the wheel. Thus, the B-width portion acts as a bottleneck.

With the turbine assembly of the present application, however, only thefirst volute feeds exhaust gas into the B-width portion, and hence theoutlet portion of the first volute can have an axial width substantiallyequal to the B-width, whereas in a conventional twin-scroll turbine,both scrolls' outlet portions (and the dividing wall between them) mustfit into the B-width. The second volute feeds exhaust gas into the finalportion of the wheel, closer to the throat. The advantage of thisarrangement is that the volutes can pass a larger amount of flow, whichall still goes into the turbine wheel.

In one embodiment described herein, the valve cavity of the valve isdefined by an integral portion of the turbine housing. The valve cavityis spatially located between the exhaust gas inlet of the turbinehousing and the bore of the turbine housing. The bypass passage isspatially located between the valve cavity and the bore of the turbinehousing. The valve member is mounted in the turbine housing so as to berotatable about a pivot point when moving between the first (closed),second (partially open), and third (fully open) positions.

The valve cavity has a proximal end adjacent the bypass passage and anopposite distal end, and a valve seat is defined by the turbine housingat the distal end of the valve cavity, the valve member having a distalend portion engaging the valve seat in the closed position. The valvemember has a proximal portion configured such that in the second(partially open) position of the valve member the proximal portionoccupies and substantially closes off the bypass passage. The valve isconfigured and arranged such that in the third (fully open) position thevalve member is completely withdrawn from the valve cavity and thebypass passage.

In one embodiment, the valve member can be arranged such that the second(partially open) position and/or the third (fully open) position isadjustable for regulating flow rate through the second volute and/orbypass passage.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

Having thus described the disclosure in general terms, reference willnow be made to the accompanying drawings, which are not necessarilydrawn to scale, and wherein:

FIG. 1 is a perspective view of a turbine assembly in accordance withone embodiment of the present invention;

FIG. 2 is a perspective view of the turbine assembly of FIG. 1, whichhas been sectioned to show internal details;

FIG. 3 is a sectioned side view of the turbine assembly with the valvein a closed position;

FIG. 4 is a sectioned side view of the turbine assembly with the valvein a partially open position;

FIG. 5 is a sectioned side view of the turbine assembly with the valvein a fully open position; and

FIG. 5A is a sectioned side view of the turbine assembly on an enlargedscale relative to FIG. 5.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention now will be described more fully hereinafter withreference to the accompanying drawings in which some but not allembodiments of the inventions are shown. Indeed, these inventions may beembodied in many different forms and should not be construed as limitedto the embodiments set forth herein; rather, these embodiments areprovided so that this disclosure will satisfy applicable legalrequirements. Like numbers refer to like elements throughout.

FIGS. 1-5 illustrate a turbine assembly 10 in accordance with oneembodiment of the invention described herein. The turbine assemblyincludes a turbine housing 12 having an exhaust gas inlet 14 thatreceives a stream of commingled exhaust gases from the cylinders of aninternal combustion engine. The turbine assembly further comprises aturbine wheel 20 mounted within the turbine housing and connected to ashaft 22 whose opposite end is connected to a compressor (not shown)when the turbine assembly is part of a turbocharger for boostingperformance of the engine. The turbine housing defines a bore 16 thatextends along an axial direction generally parallel to the rotation axisof the turbine wheel 20. After exhaust gases have passed through theturbine wheel, the gases are discharged in the axial direction throughthe bore 16.

The turbine housing 12 further comprises a twin volute having a firstvolute 24 and a second volute 26 that surround the turbine wheel 20. Thevolutes 24, 26 are divided and separated from each other by a dividingwall 28. The volutes 24, 26 receive exhaust gas from the exhaust gasinlet 14 and feed the gas into the turbine wheel. Thus, the first volute24 has an outlet portion 25 (FIG. 5A) at a radially inner side of thevolute, through which exhaust gas is discharged from the volute into theturbine wheel. Similarly, the second volute 26 has an outlet portion 27through which exhaust gas is discharged from the volute into the turbinewheel.

Although not visible in the figures, the exhaust gas inlet 14 isconnected to the first volute 24 such that the first volute alwaysreceives exhaust gas from the engine. However, the second volute 26receives exhaust gas only during higher-flow operating conditions wherethe first volute 24 alone is inadequate for passing the flow. In thisregard, the turbine assembly 10 includes a valve 30 operable to eitherprevent or allow exhaust gas flow into the second volute 26. In theillustrated embodiment, the valve 30 is integrated into the turbinehousing 12, but alternatively it could be separate from the turbinehousing (e.g., integrated into an exhaust manifold of the engine). Thevalve 30 includes a valve cavity 32 that is connected to the exhaust gasinlet 14 for receiving exhaust gas therefrom, and a valve member 34 thatinteracts with the valve cavity 32 for regulating flow of exhaust gasfrom the valve cavity. Although not visible in the figures, the valvecavity 32 is connected to the second volute 26. In partially and fullyopen positions of the valve member 34, exhaust gas is able to flow fromthe valve cavity 32 to the second volute 26, but in the closed positionof the valve member 34 exhaust gas is prevented from flowing to thesecond volute 26.

The valve 30 also includes a valve seat 36 formed by a portion of theturbine housing and located at a distal end of the valve cavity 32. Anopposite proximal end of the valve cavity 32 connects with a bypasspassage 40 that extends into the bore 16 at a point downstream of theturbine wheel 20. The valve member 34 is a swing-type waste gate thathas a tubular proximal portion 34 a affixed to one end of an arm 42, theopposite end of the arm being pivotally connected to the turbine housingsuch that the valve member 34 is rotatable about a pivot axis. Theproximal portion 34 a of the valve member is sized so that itsubstantially fills and closes off the bypass passage 40 when insertedthrough the bypass passage into the valve cavity 32, as shown in FIGS. 3and 4. The valve member 34 further comprises a distal portion 34 battached to the end of the proximal portion 34 a. The distal portion 34b is configured to seat against the valve seat 36 in a substantiallysealed manner when the valve member 34 is inserted fully into the valvecavity 32, as shown in FIG. 3. This is the closed position of the valvemember 34, in which the valve member prevents exhaust gas from flowingto the second volute 26 or to the bypass passage 40.

When the valve member 34 is rotated about its pivot axis from theposition in FIG. 3 to the position shown in FIG. 4 (the partially openposition), the distal portion 34 b unseats from the valve seat 36 andthus exhaust gas can flow into the valve cavity 32 and into the secondvolute 26. However, the engagement of the proximal portion 34 a of thevalve member 34 in the bypass passage 40 substantially prevents anyexhaust gas from flowing through the bypass passage. Thus, in thepartially open position of the valve, the first and second volutes 24,26 feed substantially all of the exhaust gas into the turbine wheel andsubstantially none of the exhaust gas bypasses the turbine wheel.

When the valve member 34 is further rotated about its pivot axis fromthe position in FIG. 4 to the position shown in FIG. 5 (the fully openposition), the valve member 34 is entirely withdrawn from the valvecavity 32 and bypass passage 40, and therefore exhaust gas can flow fromthe valve cavity 32 to the second volute 26 as well as through thebypass passage 40 into the bore 16. Thus, in the fully open position ofthe valve, both volutes feed exhaust gas into the turbine wheel, and inaddition some exhaust gas bypasses the turbine wheel.

The valve 30 thus has at least three positions (closed in FIG. 3,partially open in FIG. 4, and fully open in FIG. 5) for regulating flowthrough the turbine assembly 10. In some embodiments, the valve can havemore than three positions. For example, there can be various degrees ofopenness of the valve in the partially open position—i.e., the partiallyopen position can be adjustable so that a greater or lesser amount offlow is passed to the second volute 26, and this adjustment can be made“on the fly” (e.g., as regulated by a controller that controls anactuator that supplies the motive force for rotating the valve member 34about its pivot axis) depending upon the needs of the particularoperating condition of the engine. Similarly, the fully open position ofthe valve member 34 can be adjustable for regulating flow through thebypass passage 40.

In accordance with the invention at least in certain embodimentsthereof, the first volute 24 and second volute 26 are of differentsizes. In particular, the first volute 24 has an A/R ratio less thanthat of the second volute 26. Additionally, the first volute 24 has itsoutlet portion 25 positioned to feed exhaust gas into the B-widthportion 20 a of the turbine wheel 20, while the second volute 26 has itsoutlet portion 27 spaced axially downstream of the first volute's outletportion for feeding exhaust gas into the contour portion 20 b of theturbine wheel. The turbine wheel can be a non-splittered turbine wheelas illustrated, or a splittered turbine wheel having full bladesalternating with splitter blades.

A method for configuring and operating a turbocharged internalcombustion engine system in accordance with one embodiment of thepresent invention comprises the steps of:

-   -   providing a turbocharger having a turbine assembly 10 of the        type described above;    -   providing an internal combustion engine having a plurality of        engine cylinders;    -   supplying commingled exhaust gases from all of the engine        cylinders into the exhaust gas inlet 14 of the turbine housing;    -   positioning the valve member 34 in the first (closed) position        when engine exhaust gas flow rate is in a first range, such that        the commingled exhaust gases are supplied to the first volute 24        only; and    -   positioning the valve member 34 in the second (partially open)        position when engine exhaust gas flow rate is in a second range        greater than the first range, such that the commingled exhaust        gases are supplied to the first volute 24 and the second volute        26.

When the valve further comprises a bypass passage 40 connected from thevalve cavity 32 to the bore 16 downstream of the turbine wheel 20, andthe valve member 34 is movable into a third position allowing thecommingled exhaust gases to flow to the first and second volutes 24, 26and through the bypass passage 40 to the bore 16, the method can furthercomprise the step of positioning the valve member 34 in the thirdposition when engine exhaust gas flow rate is in a third range greaterthan the second range, such that the commingled exhaust gases aresupplied to the first volute 24, the second volute 26, and the bypasspassage 40.

The invention offers advantages over a conventional single-volute ortwin-scroll turbine assembly. With those conventional turbineassemblies, a compromise in design must be made between the desire for alow minimum flow rate at low engine speeds and the desire for a highturbine efficiency at high engine speeds. A conventional single- ortwin-volute turbine assembly specifically designed to have a low minimumflow rate tends to be poorer in turbine efficiency at high flow (highengine speed), relative to a similar turbine assembly specificallydesigned for good efficiency at high flow. Conversely, if the turbineassembly is designed for good efficiency at high flow, then it tends tohave a higher minimum flow rate than a similar turbine assembly designedfor the low-flow condition. However, with the turbine assembly of thepresent invention, the sequential activation of the two volutes 24 and26, together with the ability to specifically design the volutes forlow- and high-flow conditions, respectively, result in both a lowerminimum flow rate and an improved high-flow efficiency, relative to asimilar conventional single- or twin-scroll turbine assembly.

Many modifications and other embodiments of the inventions set forthherein will come to mind to one skilled in the art to which theseinventions pertain having the benefit of the teachings presented in theforegoing descriptions and the associated drawings. Therefore, it is tobe understood that the inventions are not to be limited to the specificembodiments disclosed and that modifications and other embodiments areintended to be included within the scope of the appended claims.Although specific terms are employed herein, they are used in a genericand descriptive sense only and not for purposes of limitation.

1. A turbine assembly of a turbocharger for use with an internalcombustion engine, the turbine assembly comprising: a turbine housinghaving a single exhaust gas inlet for receiving exhaust gas from theengine, a bore for conducting a flow of exhaust gas out of the turbinehousing in an axial direction, and a twin volute surrounding the bore,the twin volute comprising a first volute and a second volute that isdivided and separated from the first volute, the exhaust gas inlet beingconnected to the first volute but not to the second volute; a turbinewheel rotatably mounted in the bore; the first volute having an outletportion configured to direct exhaust gas into a first portion of theturbine wheel; the second volute having an outlet portion configured todirect exhaust gas into a second portion of the turbine wheel locateddownstream of the first portion of the turbine wheel with respect to theaxial direction; and a valve arranged in the turbine housing downstreamof the exhaust gas inlet so as to receive exhaust gas therefrom, thevalve defining a valve cavity connected to the second volute but not tothe first volute, the valve further comprising a valve member movablebetween a first position allowing exhaust gas to flow to the firstvolute but preventing exhaust gas from flowing from the valve cavity tothe second volute, and a second position allowing exhaust gas to flow tothe first volute and to flow from the valve cavity to the second volute.2. The turbine assembly of claim 1, wherein the outlet portion of thefirst volute is positioned to feed exhaust gas into a B-width portion ofthe turbine wheel, and the outlet portion of the first volute has anaxial width substantially equal to that of the B-width portion.
 3. Theturbine assembly of claim 2, wherein the outlet portion of the secondvolute is spaced axially downstream of the B-width portion.
 4. Theturbine assembly of claim 3, wherein the B-width portion of the turbinewheel leads into a contour portion of the turbine wheel, and the contourportion leads into a final portion of the turbine wheel, the turbinewheel having a throat located within the final portion, and wherein theoutlet portion of the second volute is positioned to feed exhaust gasinto the final portion of the turbine wheel upstream of the throat. 5.The turbine assembly of claim 1, wherein the second volute has a greaterA/R ratio than does the first volute.
 6. The turbine assembly of claim1, wherein the valve cavity is spatially located between the exhaust gasinlet of the turbine housing and the bore of the turbine housing.
 7. Theturbine assembly of claim 6, wherein the valve member is mounted in theturbine housing so as to be rotatable about a pivot axis when movingbetween the first and second positions.
 8. The turbine assembly of claim7, wherein the valve member is a swing-type waste gate.
 9. The turbineassembly of claim 1, wherein the valve further comprises a bypasspassage connected from the valve cavity to the bore downstream of theturbine wheel, and wherein the valve member is movable into a thirdposition allowing exhaust gas to flow to the first and second volutesand through the bypass passage to the bore.
 10. The turbine assembly ofclaim 9, wherein the bypass passage is spatially located between thevalve cavity and the bore of the turbine housing.
 11. The turbineassembly of claim 10, wherein the valve cavity has a proximal endadjacent the bypass passage and an opposite distal end, and a valve seatis defined by the turbine housing at the distal end of the valve cavity,the valve member having a distal end portion engaging the valve seat inthe closed position.
 12. The turbine assembly of claim 11, wherein thevalve member has a proximal portion configured such that in thepartially open position of the valve member the proximal portionoccupies and substantially closes off the bypass passage.
 13. Theturbine assembly of claim 12, wherein the valve is configured andarranged such that in the third position the valve member is completelywithdrawn from the valve cavity and the bypass passage.
 14. The turbineassembly of claim 9, wherein the valve member is arranged such that thethird position is adjustable for regulating flow rate through the bypasspassage.
 15. The turbine assembly of claim 1, wherein the valve memberis arranged such that the second position is adjustable for regulatingflow rate through the second volute.
 16. The turbine assembly of claim1, wherein the turbine wheel is a splittered turbine wheel.
 17. Aturbine assembly of a turbocharger for use with an internal combustionengine, the turbine assembly comprising: a turbine housing configuredfor receiving engine exhaust gas, the turbine housing defining a borefor conducting a flow of exhaust gas out of the turbine housing in anaxial direction, and a twin volute surrounding the bore, the twin volutecomprising a first volute and a second volute that is divided andseparated from the first volute; a turbine wheel rotatably mounted inthe bore, the turbine wheel defining a B-width portion followed in theaxial direction by a contour portion, the contour portion being followedin the axial direction by a final portion, the turbine wheel furtherdefining a throat located in the final portion; the first volute havingan outlet portion configured to direct exhaust gas into the B-widthportion of the turbine wheel; the second volute having an outlet portionconfigured to direct exhaust gas into the final portion of the turbinewheel upstream of the throat; and a valve arranged to receive engineexhaust gas and regulate flow of the exhaust gas into the first andsecond volutes.
 18. A turbine assembly of a turbocharger for use with aninternal combustion engine, the turbine assembly comprising: a turbinehousing having an exhaust gas inlet for receiving exhaust gas from theengine, and a bore for conducting a flow of exhaust gas out of theturbine housing in an axial direction; a turbine wheel rotatably mountedin the bore; the turbine housing defining a twin volute surrounding theturbine wheel, the twin volute comprising separate first and secondvolutes for feeding exhaust gas to the turbine wheel, the exhaust gasinlet being connected to the first volute; and a valve integrated in theturbine housing downstream of the exhaust gas inlet so as to receiveexhaust gas therefrom, the valve defining a valve cavity connected tothe second volute but not to the first volute, the valve furthercomprising a valve member movable between a first position allowingexhaust gas to flow to the first volute but preventing exhaust gas fromflowing from the valve cavity to the second volute, and a secondposition allowing exhaust gas to flow to the first volute and to flowfrom the valve cavity to the second volute; wherein the valve cavityextends along an axis and is spatially located between the exhaust gasinlet of the turbine housing and the bore of the turbine housing, andthe valve member is mounted in the turbine housing so as to be rotatableabout a pivot point, thereby moving the valve member along the axiswithin the valve cavity.
 19. A method for configuring and operating aturbocharged internal combustion engine system, comprising the steps of:providing a turbocharger having a turbine assembly according to claim 1;providing an internal combustion engine having a plurality of enginecylinders; supplying commingled exhaust gases from all of the enginecylinders into the exhaust gas inlet of the turbine housing; positioningthe valve member in the first position when engine exhaust gas flow rateis in a first range, such that the commingled exhaust gases are suppliedto the first volute only; and positioning the valve member in the secondposition when engine exhaust gas flow rate is in a second range greaterthan the first range, such that the commingled exhaust gases aresupplied to the first volute and the second volute.
 20. The method ofclaim 19, wherein the valve further comprises a bypass passage connectedfrom the valve cavity to the bore downstream of the turbine wheel, andwherein the valve member is movable into a third position allowing thecommingled exhaust gases to flow to the first and second volutes andthrough the bypass passage to the bore, the method further comprisingthe step of: positioning the valve member in the third position whenengine exhaust gas flow rate is in a third range greater than the secondrange, such that the commingled exhaust gases are supplied to the firstvolute, the second volute, and the bypass passage.
 21. The method ofclaim 19, further comprising the step, when engine exhaust gas flow rateis in the second range, of varying the second position of the valvemember to regulate flow rate of the commingled exhaust gases into thesecond volute.
 22. The method of claim 20, further comprising the step,when engine exhaust gas flow rate is in the third range, of varying thethird position of the valve member to regulate flow rate of thecommingled exhaust gases into the bypass passage.